It is nowadays known to use a pontoon crawler track assembly as described above as a crawler-track-driven undercarriage particularly in working machines operating in water, such as excavators. A working machine, being equipped like this, is transported to its operating site usually by road as a so called extra wide transportation, which always requires extra arrangements including separate warning vehicles etc. After the operation the working machine is being returned to its maintenance point, whereby a usual undercarriage is being replaced to the same, in case the next operation is related to usual ground excavation. This is why the measures related to a preliminary preparation and transportation of a working machine, being utilized in water, are first of all very laborious to perform and on the other hand get disproportionately expensive particularly due to those special arrangements needed for road transportations.
Furthermore in U.S. Pat. No. 6,315,622 there has been presented a pontoon crawler track assembly suitable for the above purpose, which comprises a mounting frame, which is put together from parts in a way that it includes a middle part, to be attached e.g. to a fastening beam of an excavator, and furthermore fastening parts, to be attached to the ends of the middle part by screw joints, in order to fasten the actual pontoon members equipped with crawler tracks. One meaning of the above solution is that by altering particularly the lengths of the fastening parts for the pontoon members, it is possible to vary the breadth of the pontoon crawler track assembly, acting as an undercarriage of an excavator, to be most suitable for each purpose.
The solution according to U.S. Pat. No. 6,315,622 does not bring about any significant advantage with respect to the problems, being explained before, because it is based on the fact that the undercarriage must be first of all put together manually from separate parts by applying several bolt joints, which must be carried out in practice usually indoors. On the other hand it must still be transported separately in its operating breadth to an installation site or together with the excavator, while being attached to the same. This is why, also in connection with this type of solution, there is still a need to use extra wide road transportations. In addition to that, for each differing operating breadth of the undercarriage, fastening parts having deviating measures must be manufactured/stored.